I had begun writing a book about my family history, and I was talking to my mother about why she was attracted to my father when she met him in the late 1950s. My father was a farmer, and I was vaguely expecting - or, hoping - that she would say something about his patience and understanding, or his way with animals. Those were some of the qualities that I found striking in him; qualities that, I realise now, I was focusing on because I thought they would make him seem like a farmer in a book ought to seem. A quote from my mum would point them up nicely.

"Well," she said. "He was very good-looking."

"Right," I said. "But what else?"

"Umm, he was very tall as well. I remember liking how tall he was."

"Yes, yes, OK Mum, but what about his personality?"

"I can't really remember ... he used to warm my feet for me, that was nice. Oh, and I know ... " Suddenly she brightened up, apparently recalling something. Great, I thought, here it comes; his gentleness when he delivered a calf, his calm appraisal of the weather, the sense of timelessness as you watched him striding the furrows ...

"He was a very good kisser. What you young lot would call a passionate kisser today. And he always used to call me 'sugar', I loved that. I thought it was really romantic and ..."

"Romantic?" I gave up trying to keep my facial expression neutral. "Dad?"

"Ooh, I remember when we used to go to the pictures, it was ..."

"Right, thanks Mum! Tell you what, let's have a cup of tea, and then, er come back to it."

That exchange took place right at the start of my research, and it taught me two things. First, asking your parents about their love lives is generally a bad idea, and second, even your closest relatives may think of people and events from your shared past in ways utterly incomprehensible to you. The first you can live with, but the second means that trying to write down your family history can become somewhat troublesome.

The book I was writing had been sold to its publisher as the history of a farm and the surrounding Yorkshire countryside. However, as our farm was an old-school family affair on which my brother and sister, mother, friends, neighbours and I worked in our spare time, I couldn't tell its story without telling ours.

I should explain here that the story was as messily up and down as most families' stories. The farm had been ours for generations, and as the eldest son I should have taken it on. However, lacking any practical abilities, I ran off to London to become a journalist; my sister, Helen, became a teacher, and it was left to my brother, Guy, to work with my parents. Together they struggled financially, and had to sell up in the late 90s.

When I came to record it all, I found it easy enough to establish places and dates, but stunningly difficult to get anyone to agree on details. One of my most potent memories, for example, is of taking charge of some ill pigs when I was about 17. I thought by saving some of them I might redeem my klutzy image, and built them a special pen, and spent my spare time feeding them. They all died, and when I told my dad the last one had gone, I realised he had known this would happen, and that he would not have let Guy, who was being trained seriously, persist in such a sentimental illusion; in short, it meant everyone had realised before I did that I'd be leaving.

Did my brother, father or mother remember the sick pigs as a major turning point, too? Er, no: they did not, in fact, remember them at all. The only person who did was Helen. She had helped me with them herself - only for me, in my egocentric self-absorption, to subsequently forget about her. After months of this, and of the challenges to long-held ideas about family members and myself, I realised how separate we all are, in the end. It's quite a bleak feeling, and it means that you can only ever tell your own story, not everyone else's.

Even after accepting that little bit of everyday existentialism, you face the problem of showing people what your family is like. Recording what they did and said is the best method, but this is difficult if, in the British way, they don't say anything. My family was perhaps a particularly hard case because it fits the Yorkshire farming stereotype very well, but the ways we reveal feelings are probably common; the glance away, the silence left a beat too long, the deliberate gruffness meant to convey affection. Ask any of the men a direct personal question and they deflect it like Michael Vaughan flicking a ball to the boundary. When I asked my brother how he felt about the sale that meant the loss of his job, and 10 generations of work, he said "Well, you get over it."

Ironically, it was in writing about Guy that I found a way to deal with this, and learned something else about family life in the process. My brother is a living textbook definition of Yorkshire stoney-facedness, and when he does speak his words tend to have a different meaning to the literal one. At one point I thought I had so little material that I was going to have to give up altogether, and then one day in frustration I just typed: "Guy prefers not to speak at all. He communicates chiefly through the eyebrow raise, the shrug, and the brief lift of the chin. When he greets you at a train station by asking: 'What the fuck you got in this suitcase?' it is his way of saying hello, how are you?"

A few days later, it dawned on me - Yorkshire farmers might tend to be extreme cases, but this is true to a certain extent for all families. Being so familiar and intimate with each other, we communicate well beyond the literal. We have learned to read each others' facial expressions like meteorologists reading a sky, and we have an elaborate set of codes that in later life will amuse, baffle and infuriate those friends and lovers whom we invite into the fold. ("I'm sure your mother didn't mean that ..." "Shut up! You don't know her!")

Perhaps the most impenetrable codes will be those that allow us to talk obliquely, referring to things, people and events in ways that imbue them with extra layers of meaning. This is not limited to families, of course, but it is chiefly in family life, where we all know so much about one another, that it happens unconsciously and accidentally.

For example, the moment I realised how much stuffing the loss of the farm had knocked out of my dad was not during the auction, but months afterwards when my mum asked him if he wanted to watch a western. They love westerns in the way some people of their generation love rock'n'roll, and their courtship and subsequent married life had involved watching at least two a week. That evening he said he wasn't bothered, because, "We've seen 'em all anyroad. You always know how it's going to end." To anyone else, a fair comment on an old film genre; to his wife and children, the sign that he had momentarily lost interest in himself and the world.

What all this taught me was that the real truth of family life is rarely experienced at those moments when you are conscious of it. Looking back, you will remember meaningful moments not from anniversary parties, or events caught on tape and photographs, but from moments when you were looking the other way; the day you taught the dog to sit up, the walk to the bus stop from the cinema singing the songs from the film together, the summer you nursed the sick animals with your little sister. Of course the memories will be gnawed and twisted by time, but it will be the experiences whose meaning was bestowed by the togetherness of friends and family that endure. I don't want to sound schmaltzy, but it seems to me that when so many businesses are trying to sell family happiness to us in the shape of a themepark ticket or cuddly toy, this is worth bearing in mind.

People often ask me if my family minded being written about. The answer is not really. My mum didn't like the inclusion of swearwords, or the detail about her liking my dad to rub her feet, and I worry about some chapters where I made my poor, slandered sister sound stern when in fact she was funny. To be honest I shall regret this latter point for the rest of my life, and because of it and the other problems, I would tell anyone thinking of doing a family memoir to think carefully about it before beginning.

I certainly find myself being reminded that you can tell only your story and not the whole family's. When the book was published I was invited to talk about it at a Yorkshire Post literary luncheon in Harrogate. I took my brother, and afterwards became separated from him in the throng. I was a bit worried about how he'd get on with the befrocked and suited county set, but afterwards, as he drove us home in his truck, he said he'd had a good time. There was just one thing that puzzled him, he said. "What the fuck does 'taciturn' mean? People kept telling me that's what I was, and I didn't have a clue what they meant."